There is a trigger to turn off access to the Home City.
Yes, you need either a Town Center or an Outpost or Fort to receive shipments from the Home City. If you do a RPG scenario with no TC but leave the Home City available, you will still be accruing experience -- you'll see it gathering and hear sound notifications as you earn shipments.
Whether you turn off the Home City completely or choose to not give the player a drop-off site would depend on the effect you want. For example, it might be cool to let the player gather experience, then have an event in the scenario where he gets access to a TC/Fort/Outpost and then can spend his shipments. Hmmm, maybe I'll use that ...[This message has been edited by ES_GeneralZod (edited 06-06-2005 @ 06:13 PM).]